The present invention relates to a seat assembly in a power machine. More particularly, the present invention relates to an operator presence sensing system sensing operator presence in a seat of a power machine.
Vehicle seat switches have been used in the past in order to determine the presence of an operator in a power machine. Such seat switches typically involve a spring, or some type of bias member which biases the seat of the power machine in an upward direction. A switch is generally located beneath the seat and is actuated when a load is applied to the seat, and deactuated when the load is removed from the seat. The switch is typically coupled to an electrical circuit which provides a signal indicative of whether the load is applied to the seat.
In addition, some conventional seat switch mechanisms are configured to operate with seats which pivot in a fore and aft direction, or seats which move in a substantially vertical direction under an operator load. Further, such seats are normally adjustable in the fore and aft (generally horizontal) direction to accommodate various operator sizes. Thus, in order to actuate the seat switch, the operator has been required to load the seat with a net weight sufficient to provide downward movement of a portion of the seat, about the fore and aft pivot, to actuate the seat.
When the machine is operated by an operator of small physical stature, that operator typically requires the seat to be adjusted forward. This moves the effective net weight of the operator forward relative to the pivot point of the seat. The combination of a lighter weight operator exerting a smaller load on the seat, and the seat being moved forward (for a front pivot seat) reduces the positive downward force bias on the seat that is necessary to keep the seat switch in operating position.
Further, it is common for the operator of such a machine to lean forward to line up and adjust elevation of a loader lift arm attachment mounting frame with the attachment frame of a tool, such as a bucket, which is to be used on the machine. As the operator leans forward, particularly the smaller or shorter operator, the seat switch can temporarily disengage certain operations of the vehicle. Thus, it is inconvenient for such operators, during mounting of an attachment, to concentrate on aligning the lift arm attachment mounting frame with the attachment frame on the tool, while also concentrating on keeping enough weight on the seat to keep the seat switch engaged.